Ventilation louvers are commonly used on the gable ends of houses and other buildings. The purpose of such louvers is to permit ventilation of attics and other spaces in buildings by providing a set of screened openings through which air can circulate. Typically louvers are made in a variety of geometric shapes, with shape selection being largely a matter of aesthetic preference. Usually the louvers are made of blow molded plastic (but sometimes of wood), normally with a polygonal sidewall (of desired shape) with a radially outwardly extending circumferential flange at the bottom of the sidewall.
Installation of a louver in a building wall involves cutting a hole in the underlying sheeting material, and then nailing or screwing the louver flange in place on the perimeter of the hole. Next, the wall (including the louver flange) is covered with a desired exterior face material which can be brick, aluminum siding, vinyl siding or other material.
When a siding material is used, the siding must be cut at the construction site so that it abuts against the sidewall of the louver. Since the cuts are never perfect, this typically leaves gaps between the ends of the siding and the sidewall of the louver. Such gaps are unsightly and in addition wind, rain and snow can blow into them, causing leakage. Therefore the gaps must be covered.
In current practice, siding edge strips are cut to length and secured to the sidewall of the louver to cover the cut ends of the siding. This is time consuming and difficult, and therefore expensive. Caulking is also sometimes used, but frequently caulking cannot fill and cover the spaces involved, and in addition caulking tends to shrink and discolour and is therefore unsatisfactory.